Inflammation and parenchymal tissue damage are hallmarks of pancreatitis. In particular, severe necrosis is a major complication of the disease. Over the past decade, significant progress has been achieved in understanding the mechanisms of the inflammatory response of pancreatitis. In contrast, very little is known about the mechanisms of pancreatic acinar cell death. Mechanisms of necrosis are largely unknown. Key signals mediating apoptosis have been established; however, their roles in disease processes remain obscure, and they have not been investigated in pancreatitis. The role of cell death pathways in pathologic trypsin activation, an important marker of tissue damage in pancreatitis, has not been explored. Our preliminary data indicate that key necrotic and apoptotic mechanisms: poly (ADP-ribose) polymerase (PARP), mitochondrial dysfunction, caspases (specific cysteine proteases), and the transcription factor NFkappaB are activated in experimental models of pancreatitis and in pancreatic acinar cells stimulated with cholecystokinin (CCK). For the present application, we hypothesize that in pancreatitis, necrotic and apoptotic signaling pathways are interrelated. Activation of PARP and mitochondrial de-energization leads to ATP depletion and necrosis. On the other hand, effector caspases mediate apoptosis and limit necrosis by inactivating PARP and trypsin. NFkappaB negatively regulates effector caspases and, thus plays an anti-apoptotic role in pancreatitis. Thus PARP, mitochondrial dysfunction, caspases, and NFkappaB play central roles in determining the balance between apoptotic versus necrotic type of acinar cell death and the severity of pancreatitis. We propose the following specific objectives for the present application: 1). Determine the role of PARP in necrosis and apoptosis in experimental pancreatitis and in vitro, in pancreatic acini stimulated with CCK. 2). Determine the role of mitochondrial dysfunction in necrosis and apoptosis in experimental pancreatitis and in vitro, in pancreatic acini stimulated with CCK. 3) Determine the role of caspases in necrosis, apoptosis, and trypsin activation in experimental pancreatitis and in vitro, in pancreatic acini stimulated with CCK. 4). Determine the role of NFkappaB in necrosis and apoptosis in experimental pancreatitis and in vitro, in pancreatic acini stimulated with CCK. Measurements to achieve these goals will include measures of pancreatitis, morphologic characterization of apoptosis and necrosis, intrapancreatic activation of caspases and trypsin, cytochrome c release, mitochondrial membrane potential, ATP levels, and NFkappaB activation by using Western blot and gel shift analyses, enzymatic and fluorimetric assays. The result of the experiments in the proposed specific objectives will be delineation of key molecular mechanisms regulating necrosis and apoptosis in acute pancreatitis, which will lead to novel therapeutic strategies to treat the disease.